TonyD89

iTrader: (10)

Reallity is two hits per rev.

If it was not geared, three? WTF!

The only, commercially availlaby, currently raced, and still mass produced, rotary engine gets two hits per rev at 1.3 liters for the cycle.

Till that changes, your argument is mute.

MikeC

No, you are just too stupid to understand my arguement.

KevinK2

Most theories that are not practical are not produced.

No and Yes. I see nothing that shows these handful of odd designs can make the same max hp, ie rev high like a modern boinger.


Show be a viable design, proper cooling, no leaks, competitve weight and function .... something someone may invest in, otherwise it will never exist and is just an acedemic, worthless exercise


These industrial applications have add on gearboxes, and the electric motor stands alone in it's NEMA rating. The 13B like internal gearing would have to occur inside the nema motor, which it never does. You can buy gearmotors, but these are just motors drive small reducers in the same housing. The motor portion stands alone in it's rating

KevinK2

NEVER the right response from a person of knowledge.

TonyD89

iTrader: (10)

Whatever. I'm done.

KevinK2

Easier said than produced in a viable way. Reminds me of the quad rotor engine with multi hinged rotors. Hope you can build a fast or slow cycle engine that is viable and is better in some way than current engines rated 4 stroke engines at say 250 hp max, with same "pump based" displacement rating.

MikeC

Tony was trying to invoke such a response. Unfortunately I was silly enough to give him what he wanted.

MikeC

Just to sumarise, I believe you understand everything I've said but just don't buy it based on the fact that such engines are not mainstream?

Well, I really don't see why the engine would need to be mass produced and become mainstream for it to have an effect on this discussion. Why does it suddenly going from 1% usage to 99% usage make any difference? The 2 revs method can be shown to be flawed with these engines and I have shown that I can tune the 2 revs displacement to be whatever I want it to be. How can this method be any more solid based on whether these engines are in common use or not? Engine like this do exist, many planes in WW2 did have radial engines where the pistons rotated and they produced several hundred horsepower. Does the fact the engine was used in WW2 and is no longer used have any bearing? No way!

And, one such engine does exist and is in mainstream use, the 13B rotary.

MikeC

I've just done a bit of a google search and found engines similar to what I've described are more common than I thought and are currently used and being developed today. There's also been many examples in history as well, especially for airplanes and motor cycles. Apparently for new engines the cam drive has some appeal because it can be designed so the piston spends more time at TDC, allowing the fuel to burn more thouroughly.

the 'rad-cam' engine described on this page is a piston motor that uses cams instead of a crank to take drive from the pistons. It fires each piston twice per rev:
http://translate.google.com/translat...language_tools

God knows what is happening inside this 2000hp bmw engine:
http://www.enginehistory.org/German/BMW/BMW801.pdf

Cam driven engine that hits TDC 3 times per rev. This is another design that could have the displacement via 2 revs 'tuned' to whatever the designer liked:
http://peswiki.com/index.php/Directo...m-Drive_Engine

old motorbikes with piston rotating with the wheels:
http://translate.google.com/translat...language_tools

Rotating radial aircraft engine:
http://www.keveney.com/gnome.html

Another cam driven variation:
http://www.regtech.com/rotaryprinciple.html

The MYT engine:
http://www.angellabsllc.com/animation.html

TonyD89

iTrader: (10)

Mike I'm sorry if I got a little short with you. I feel you are obsessing over a non issue. You have convinced me that the displacement for piston engines has been wrong for a lot of years. I believe Mazda more accurately labeled the displacement of thier engine.

It's all about the power stroke when the day is done. And how many you can get per crank rev. I've also seen the engines in your links before and the "quad-rotor" posted by kevin. Regardless of the configuration, the engine will burn a fixed displacement or multiples of per crank shaft rev.

That said. Your argument would become much more important if, say, the 13b could operate at three times the RPM of a simalar displacement piston engine (with all the driveability of the current factory produced engine, 7000 RPM redline in my FC. I know the Renisis is 9000). Imagine if a Wankle coul be as drivable as the current one yet go to 21,000 RPM! I would side with your argument. I think that may be the true advantage of some of these other designs.

I believe calling the 13b a 3.9 is just as wrong as calling a 350 a 350. Should be called a175 unless it's a 2-cycle. But in this way your argument is valid.

Lastly, you have to take in practical application. The tach in both my NA and turbo S5's says redline at 7,000. I know electronic cut-off is higher. My Honda redlines at 7,400 with cut at 8,000. Using crankshaft RPM as a base for comparison should be accurate with the 13b's displacement doubled seems like a good solution. A 2.6 liter piston engine, wether a four, six, or eight, Will only see 1.3 liters of power per crank rev. Just like the 13b.


P.S. I understand you position completely and read through all posts before replying all along the way. Even though you may think I didn't get it, I thought this was and is an interesting and thought provoking thread.

MikeC

I apologize for my response, it was childish and made me look kinda stupid.

With regards to half displacement for piston engines I see what you are saying. But it is just a convention and a reasonable means for comparison. If we changed it to be half then all engines would be rated as half and still compare to each other the same. Most likely it should be half but as a convention for comparison it works ok. If we call an s2000 and 13B 1.0litre and the rotary 1.9litre or 2.0/3.9 i'm not fussed either way.

Shouldn't it just be about how many you get? Why does it have to be per rev? The rotary gets many more power strokes than any other engine on the market by a significant margin. I know the s2000 does 9,000 rpm also but has smaller swept volume by 150cc per chamber and is a statistical outlier. If you look at the full range of engines on the market nothing with a similar sized swept volume to the rotary comes anywhere near it.

That is true but the qustion is does that relate to displacement or not.

Why is it valid at 21,000 rpm and not 9,000 though. At what point does it become valid? If the rotary did 3 times the revs of any engine on the market we would rate it as 3x the displacement. By why not at 1.5x?

The FC is a few years old now. At the time 7,000 and 8,000 rpm was pretty high revs for an engine with a 654cc swept volume. Wankel himself said that the rotary should be able have an output shaft speed 1.5x higher than any piston motor, if the s2000 can do 9000 rpm then the rotary should be able to do 13,500! This is because the times to complete each part of the stroke is the same at 13,500 rpm for the rotary as the piston motor doing 9,000 rpm. Why should that 1.5x not be taken into account for displacement?

I really meant to write that it looked like you weren't considering my points but it is good to see you are.

ronbros3

REALITY is only a concept!! and formulas are being broken everyday!! and they say Im stubborn and argumentive.. Whew!

TonyD89

iTrader: (10)

HaHa! Well then jump on in!

Roen

iTrader: (2)

I'm not a fan of this 2 times per rev argument after reading MikeC's paper on the sole fact that a 3.9L 6 cyl with 0.67 OD gearing will induct 2.6L of air per two rev's. But the displacement of that motor is still 3.9L or (1.95L according to Tony). The fact that the power/torque curve's are theoretically exact matches are what does it for me. Since the geared 3.9L and the 1.3L Rotary are pretty much functionally equivalent, the question becomes, what's the displacement of a geared 3.9L cyl motor? 3.9L or 2.6L?

KevinK2

Yes and No. I don't consider hypothetical designs that are not proven by prototype or full thermal and streass analysis to be viable to at least some degree.

The less than .01% that may or may not be consistent with a boinger regarding aspiration per rev, when evaluated by my classic pump method, are not significant.

You have not shown that to me, as I have said.

Each existing example is easily rated by the historic one-rev pump method (me) or by displacement at the end of a full engine cycle (U). Your method puts the 13B at 3.9L, mine 2.6 ..... every race organization (and wankel racer) will be more likely to side with me on this, as far as comparative displacement.

Nihilanthic

I'd just like to say that what a few people here are forgetting is the only reason 2.6 liters matters is because you're trying to compare a 3 revolution cycle motor to a 2 revolution cycle motor (4 stroke piston motor) and 4 stroke piston motors are the RULE. Rotaries are the EXCEPTION.

What 99% of the automotive world uses is what the rules are made for, conversion is the issue moreso than what a rotary actually is.

But, considering the ricey demographic that likes rotaries, calling it a "3 stroke 3.9 liter motor" doesnt mesh well with their smaller is better mentality.

KevinK2

Answers:
MikeC = 3.9L based on engine cycle
KevinK2 = 3.9L based on one true-rev pump-type displacement (gearboxes are not relevant in my displacement definition)

Question: How about the 13B
MikeC = 3.9L
KevinK2 = 2.6L
(same logic as above)

"... geared 3.9L and the 1.3L Rotary are pretty much functionally equivalent .." only when the 3.9L is penalized at it's output shaft for getting it's job done in 2 rpms while the rotary takes 3.

There is a reason the 3.5L infinity coupe makes 390 hp vs the rx8 232 ..... cubic inches, when measured correctly

KevinK2

This is an interesting design. The 3-lobe cam replaces the crank and is the output shaft. In one rev, piston goes up and down 3 times. Looks like a shaker, but for 4 stroker, each piston needs just 2/3 rev to complete a cycle (just the opposit of wankel). This is why the site says it has 3x the torque of a similar boinger. If 4 pistons, each with .65L displ, it would breath 1.5 x 4 x .65 = 3.9L PER REV. Considered valved as a pump, historic displacement rating is 7.8L ( same here as 2 rev aspiration). Based only on one engine cycle, displacement is 4 x .65 = 2.6L, although it breathes 3.9L per rev.

" This is another design that could have the displacement via 2 revs 'tuned' to whatever the designer liked "

Got no idea what you are talking about. The site says it has 3x standard engine torque, it's clear he's on the same page I am, which uses the fundamental output shaft speed. It has an engine cycle of 2/3 rev, vs 2 rev for boinger. This is a good example why the conventional method still works well, as it correctly predicts it will move 3x the air, per rev, of a similar boinger. It is a great example of another engine, like the 13B, that has internal gearing essential to it's function. The 5 lobe version has only 2/5 rev per engine cycle.

Mike, I re-read the paper on page 1. Again, great swept volume calc. But I did not find a final statement on what the 13B displacement should be, and the basis. At one point you said 1.5 x 2.6 based on event duration, and ignoring very real mechanical force limitations. Hope you can clarify this, knowing boingers rev a lot higher these days.

TonyD89

iTrader: (10)

Once again, you nail me for not being clear enough. I should have included total displacement per crankshaft revolution. Let see if this helps.

How would you compare these motors?

1) A 2.6 liter V-twin.

2) A 2.6 liter inline four.

3) A 2.6 liter V-6.

4) A 2.6 liter inline six.

5) A 2.6 liter V-8.

6) A 2.6 liter inline 8.

7) A 2.6 liter V-12.

8) A 2.6 liter inline 12.

9) A 1.3 liter rotory.


They all get 1.3 liters of fuel and air to burn per crankshaft revolution. With all due regards to Roen, I was using the two hits per rev to illustrate my belief that a 13b acts more like a four cyl. inline piston engine than a V-6.

The big difference is how it plays out in the real world! A 2.6l V-twin will never reach the effecientcy of, say, a 2.6l V-6. One hit per rev verse three. The 2.6l V-12 will find it's complication verse displacement ratio pushing it down the ladder.

The only comparison that makes sense is the six or four. I've already taken my position.

And, Mike, it isnt about the hits per rev. You are correct there. I wasn't clear.

Roen

iTrader: (2)

The only point I was trying to make is that any engine combination and size can be made to induct 2.6L of air if geared at the output shaft, which is not that hard to do.

The point about 3.9L 6-cyls, which do exist in real life, also match up in other categories, besides air per 2 revs, when geared with a 0.67 OD gear.

6 x 654 cc pistons correspond to the 654 cc chambers (rotor faces)
redline increases for both engines because of the gearing and the rotary's internal gearing
power/torque curves similar if not the same
270 degree stroke because of the gearing and the rotary's internal gearing.

I'm just saying that there are so many ways that those two engines are similar.

the only differences are what KevinK2 mentioned above.

My5ABaby

iTrader: (7)

Ok, new thought. Let's just ignore displacement all together and applaud the rotaries excellent power/weight ratio.

Just an update to this...

He wrote "Wankel Engines A to Z"

KevinK2

... and brilliant concept for a 4 stroke engine with shared combustion chambers and no recipricating parts.